1. Field of the Invention
The invention relates to outdoor conductor cable loop enclosures used in connection with buried conductor cable energy distribution systems employing conductor cables of various types such as electric cable, coaxial cable, telecommunications cable or flexible gas conducting cable.
2. Description of the Prior Art
The external transmission cables of an energy distribution system are either constructed as an aerial system or a buried system. In the aerial configuration, the cable and its associated devices are carried by and mounted on elevating means, usually the conventional utility pole. In an underground system, the transmission cables are buried, but above-ground means must be provided to permit interfacing means for distribution of the transmitted energy to the user and for other operating components.
Buried systems have become practical with the development of improved cable and methods of burying the cable, and, especially, with the development of improved insulation and covering impervious to water resulting in cables having a much longer life in subterranean service conditions.
From an operating point of view, the buried system has many advantages. Ice, snow, lightning storms, floods and other natural similar catastrophes and phenomena do not affect or interrupt service to customers. In seacoast and adjacent areas, severe corrosion problems which are encountered in aerial systems due to salt water conditions are reduced to a point where they are practically eliminated. Thus, they are more reliable, an important system characteristic. Buried systems also are more cost effective in that they have lower maintenance costs, and, lastly, they are relatively safer than the aerial type which can offer serious hazards to life and health in the event of conductor cable casualties or failures.
Besides the reliability and operating advantages of buried systems, aerial systems are in conflict with a widespread movement to improve our visual environment. It may be admitted that many aerial systems constitute an eyesore. Consequently, much effort is being expended to place overhead electrical, telephone, CATV cables and the like in underground installations. Indeed, many governmental bodies have adopted legal requirements that all new residential, commercial and industrial subdivisions be initially constructed with complete buried systems and further require that existing aerial systems currently in operation be buried on a scheduled timetable.
In an underground energy distribution system of any type, whether for power, telecommunications or other purposes, provision must be made for the interfacing of the main primary system to the end user by the interfacing of energy conductors and interfacing components. As a result, in the installation of buried cable systems, it is essential to provide access to the cable at certain predetermined locations. In a telecommunications system, such access is necessary to permit splicing of cable ends, to facilitate the attachment of branch lines to the main line, to provide means for the installation of electrical protectors to guard against lightning damage, to permit the installation of loading coils and repeaters for signal improvement and for maintenance and testing. In a fiber optic cable system, as well as the foregoing, such access is necessary for the connection of branch lines and possibly for the installation of conversion means such as an optoelectronic detector like a photo diode or a de-multiplexor or an integrated optoelectronic circuit combining the two types of devices into one integrated optoelectronic circuit. In a system for the distribution of electric power, access is needed for the installation of step-down transformers interfacing to customer service lines and for the installation of power factor correcting capacitors.
To provide access to accomplish such interfacing, it has been customary to provide a loop in the buried cable during its installation underground at predetermined locations for future use. Such cable loops are conventionally either totally buried in the ground for later retrieval by exhumation of the loop or, alternatively, the cable loops may be located above the ground.
Above-ground cable loops must be protected from mechanical damage, without which they would be subject to fracture through forceful entanglement or impact damage, as well as from brush fires or the like. As a result, above-ground cable loops should be held upright and be enclosed for their protection. In the case of power distribution systems, above-ground cable loops must be enclosed for safety reasons.
To illustrate the prior art and the problems which it has not solved, an underground electric power system is presented as an example.
In the installation of underground electric power distribution cables which serve pad-mounted step-down transformers, it is desirable to defer the actual installation of specific transformers until such time as these transformers are required for electric power service to customers. Typically, a coil or loop of cable is fashioned at each future transformer location to facilitate above-ground connection of the cable to the transformer without the necessity of splicing a tap into the buried cable.
As previously stated, it is necessary to cover or mechanically protect these loops of cable for a variety of reasons. Previously, this protection has been accomplished in various ways, such as completely burying the loop or by using a box pedestal structure to enclose an above-ground loop.
Current practice utilizes, ordinarily, a box pedestal that is normally anchored to the ground by cooperating additional structure, either by the use of one or more anchoring stakes that are driven into the ground or by the use of an outwardly turned anchoring flange extending around the bottom portion of the box pedestal which is placed a relatively substantial distance below the ground plane and over which the earth is backfilled and compacted by tamping.
These methods of protecting the cable loop present several inherent problems.
Both the completely buried loop and the box pedestal with buried flange require extensive removal, backfill and compacting of the surrounding earth during installation and retrieval of the cable loop. This practice requires the use, and presence, of additional earth moving equipment and their operators. Likewise, driven anchor stakes require special equipment for their installation and removal. This serves to increase the cost of, and prolong the time involved, in such operations.
An added problem arises in the case of enclosures employing anchoring stakes. The usual practice is to force the stakes into the ground by pounding. Where the stakes are separate from the enclosure, their location must be precisely determined prior to driving them so that the enclosure will be properly located when it is attached to its corresponding driven stake. Further, additional labor is required to properly connect and attach the enclosure to its already fixed in place anchoring stake. To solve this problem, and thus save costs, some enclosures have their anchoring stakes attached before being driven into the ground. When the stakes are already attached to their corresponding enclosure prior to their being driven, such pounding is applied to the top cover of the enclosure. In the event an unanticipated sub-soil obstruction such as a stone or other buried object is encountered by a stake, severe structural damage to the enclosure will occur, which can in some cases destroy its utility and certainly will cause it to lose its designed shape. This, too, has its cost aspects.
Further, it has been found in operating use that the channel shaped stake type pedestal ordinarily employed lacks rigidity and robustness and, thus, does not adequately protect the cable loop against vandalism or tampering.
Another problem associated with the prior art is the disturbance of the compactness of the soil around the cable loop caused by the above-mentioned digging, which increases the likelihood of undesirable settling or soil wash-out occurring after the installation of a pad-mounted transformer.
Yet another problem associated with the prior art is the difficulty involved in obtaining cable loops of the exact size desired. If the cable loop is too small to reach the interfacing device, such as a transformer, one or more jumper sections of cable must be spliced in. If too large a loop is provided, expensive cable must be pruned and, consequently, wasted. While these difficulties can be minimized by careful individual measurement of each and every loop of the many in a system, this measurement must be carefully done and requires skilled labor using special tooling and measuring gauges. This, too, has cost aspects.
Still another problem associated with the prior art is that no provisions are made in the pedestal enclosures which serve to prevent the cable loop from being bent past its minimum allowable bending radius and thereby suffering structural and conductive damage.
Besides lacking preventive structure to avoid excessive bending of the cable, the prior art teaches the use of multiple component clamping means, post means or combinations thereof for supporting the cable forming a loop. Such construction requires multiple adjustments of these components and the cable until the cable is properly positioned. This, too, requires additional time, more skilled labor and the use of special tools, with their attendant costs.
The foregoing emphasized the problems encountered by the electric power utility industry in providing an underground energy distribution system. However, it is readily apparent to those skilled in the art that these problems are not unique to the electric power industry. Similar problems are also encountered by other utility industries that employ underground energy distribution systems using flexible conductor means such as multiple conductor communications cables, coaxial cables, fiber optic cables and flexible gas pipelines.